1. Field of the Invention
This invention relates to an improved splash bar adapted for use in evaporative water cooling tower fill structure. In particular, the present invention is concerned with an extruded bar comprising a pair of arcuate in cross-section side margins and an elongated, horizontal flat top segment interconnecting the side margins, whereby the transverse cross-sectional configuration of the bar is operable to uniformly disperse water droplets falling in the fill structure and thus improve the overall efficiency of the tower.
2. Description of the Prior Art
In general, evaporative water cooling towers include an upper hot water distribution system such as an apertured distributing pan or the like and a lowermost cold water collection basin. Commonly, a splash type, water dispersing fill structure is displosed in a space between the hot water distribution system and the cold water collection basin, and the fill structure includes a plurality of elongated, horizontally arranged splash bars supported at spaced intervals by upright grid structure. Hot water discharged from the distribution pan falls onto the bars and disperses, forming smaller droplets to facilitate the cooling process. At the same time, cooling air currents are drawn through the fill structure, either by means of motor driven fans or through use of a natural draft-inducing hyperbolic tower.
The fill structure is often regarded as the single most important component of a cooling tower because the fill structure promotes interactive thermal exchange between the water and the air. As water droplets are discharged from the distribution pan, the temperature difference between the relatively warm water and the cooling air causes evaporation on the surface of the drops and cooling of the water occurs at a rapid rate. However, as the surface temperatures of individual droplets approaches the wet bulb temperature of the surrounding air, the cooling process is diminished and is dependent upon the rate of heat transfer from the inside of the drop to the outside of the drop surface. As such, it is desirable to interrupt the fall of individual drops by splashing the drops on a fill bar, thus instantly exposing new water surfaces and, in some cases, subdividing the drops into smaller droplets to increase the water surface area available for exposure to the passing air.
As can be appreciated, the characteristics of any fill structure splash bar must meet several criteria to assure satisfactory operational performance. First, the splash bar should provide consistent, predictable dispersal and break-up of the water droplets over a range of water loadings typically encountered in practice. Preferably, the descending droplets are uniformly broken into relatively fine particles in a widely divergent pattern to facilitate enhancement of the cooling process. However, the splash bar structure should cause a minimum amount of air pressure drop in order to keep fan horsepower requirements as well as operating costs at relatively low levels. Additionally, the splash bar should have sufficient structural strength to span the distance between adjacent upright grid structures, since deflection of the bars can enable the water to channel toward the low point of the bar, thereby causing unequal water dispersal throughout the passing airstream. This problem of bar deflection is more common when the bars are formed of synthetic resin material, since such bars often lose strength and stiffness when subjected to the elevated temperatures of the hot water to be cooled.
Moreover, cost is an important consideration in the selection and fabrication of splash bars. For example, a lrge hyperbolic induced-draft tower may utilize two million or so bars, each four feet in length. As a result, the use of bars formed of expensive metallic materials cannot usually be economically justified, even though metallic bars may provide adequate performance.
In the past, splash bars have often been comprised of elongated, rectangular in cross-section boards of such wood species as redwood or treated Douglas fir. However, wood splash bars, even when normally rot resistant, can deteriorate due to chemicals in the water stream. Also, wood bars present a serious fire hazard as soon as the water flow is interrupted and the moisture remaining on the bars has substantially evaporated.
To enhance the cooling performance of the fill structure, a variety of splash bar configurations have been proposed as an alternative to traditional, rectangular members. In U.S. Pat. No. 3,389,895 to Deflon, dated June 25, 1968, a number of splash bar configurations are illustrated, including an inverted V-shaped bar, a generally crescent-shaped bar, as well as a sheet material with transverse corrugations. Also, it is known that certain splash bars have comprised tubular, hollow extrusions of polyvinyl chloride, wherein a top water impinging surface is generally transversely semicircular and a bottom portion has been deformed upwardly to present a pair of spaced-apart, lower support surfaces. Although splash bars having curved, upper water impinging surfaces provide somewhat improved performance in comparison to rectangular boards at high water loadings, the performance of such curved bars decreases rapidly at relatively low water loadings. As can be appreciated, there is yet a need for an improved splash bar which optimizes cooling efficiency of the tower, in order that the fan brake horsepower requirements and the associated operating costs are minimized.